The Chinese People's Liberation Army is considering setting up an air defense identification zone that would overlap with Japan's over the East China Sea — a move that is likely to heighten tensions between the countries — according to an internal Chinese military document.

An ADIZ serves as a national defense perimeter that triggers fighter scrambles when foreign aircraft enter the zone without prior notification.

The zones are set up outside national airspace to prevent incursions by suspicious aircraft.

To date, China has not defined an ADIZ. If the country were to establish such a zone, it would be certain to overlap with Japan's as a major part of the Japanese ADIZ over the East China Sea has been set closer to China than the median line, which lies at an equal distance from the two countries.

The internal document obtained by Kyodo News shows that a Beijing-based senior air force official proposed strengthening the nation's air defense operations by setting up a Chinese ADIZ, saying neighboring countries "are insisting the validity of marine boundaries disadvantageous to our country."

The official also argued that China cannot control its maritime resources effectively without an ADIZ, the document said.

The move comes as an increasing number of Chinese aircraft have been approaching Japanese airspace after the government purchased three of the five main islands in the uninhabited Senkaku group in the East China Sea from a private owner in September last year.

In the first such intrusion, a Chinese State Oceanic Administration airplane entered Japanese airspace over the islets in December.

Such zones are set up by countries based on domestic law. There are no international rules concerning their establishment.